This application claims the benefit of Korean Application No. 2002-7007, filed Feb. 7, 2002, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an ink-jet printer, and more particularly, to an ink-jet printer capable of preventing a malfunction of a head driving unit, which occurs when ink is simultaneously discharged from a plurality of nozzles.
2. Description of the Related Art
Usually, a printer using one of a wire dot method, a heat transfer method, and an ink jet method of forming an image on a recording medium, such as printing paper or an OHP (over head project) film, uses a recording head.
The recording head of an ink-jet printer using one of the above methods has a plurality of nozzles being formed with minute discharging holes to eject ink. The ink in the nozzles is heated and expanded by heating elements disposed in corresponding ones of the nozzles and is ejected outside of the nozzles and stuck on the recording medium.
Accordingly, the ink-jet printer forms the image on the recording medium by ejecting the ink through the nozzles by selectively heating the nozzles in the recording head corresponding to the image to be recorded.
As shown in FIG. 1, a general ink-jet printer 200 includes an interface 210 receiving printing data and a control command from a host 100, an input unit 230 allowing a user to input a selection command, a storage unit 250 storing a program for driving and controlling each part of the ink jet printer 200 and the printing data, a printing unit 270 performing a printing operation, and a controller 290 controlling the entire system of the ink-jet printer 200 in accordance with the program.
A nozzle selection data signal is transmitted to a head driving device 271 of the printing unit 270 in order to drive selected ones of a plurality of nozzles of the recording head 273 in response to the printing data.
As shown in FIG. 2, the head driving device 271 includes a first data unit 21 and a second data unit 23 receiving the nozzle selection data signal having an ADDR (address) data signal ADDR and a P (primitive) data signal P_Data, a signal supply 27 having AND gates, and a nozzle driving unit 29 driving the selected nozzle among the plurality of nozzles to discharge the ink.
For example, in a case of the recording head having an nxc3x97m number of nozzles, the ADDR data signal ADDR is a data signal to select one of n number of fire groups A1-An each having an m number of nozzles, and the P data signal P_Data is a data signal to select a predetermined number of nozzles among the m number of nozzles in a corresponding one of the fire groups A1-An.
In other words, when the ADDR data signal ADDR and the P_data signal P_Data have 10 bits, then one fire group is selected among the 10 fire groups A1-A10 in response to corresponding one of the 10-bits of the ADDR data signal ADDR, and the number of the nozzles capable of simultaneously discharging the ink in response to the P data signal P-Data in the fire groups A1-A10 is 10. In other words, the entire number of nozzles of the recording head is 10xc3x9710=100.
Hereinbelow, a general operation of the head driving device 271 according to the input data signals will be described by referring to FIGS. 3A-3F.
The ADDR data signal Addr_1 and the P_data signal Data_a of the nozzle selection data signal are synchronized with a clock signal CLOCK, shifted to each bit shift register, and stored in each latch.
Then, when a load signal LOAD is input, the ADDR data signal Addr_1 and the P_data signal Data_a stored in each of the bit shift register are latched.
After that, when a fire strobe signal STRB_1 to discharge the ink in the nozzles by heating the heating element is input from the controller 290 to the signal supply 27, next ADDR data signal Addr_2 and next P data signal Data_b are stored in respective one of the n-bit shift register and the m-bit shift resistor.
Therefore, the latched data signals Addr_1 and Data_a and the strobe signal STRB_1 are input into the signal supply 27 having the nxc3x97m number of AND gates to drive the nozzle driving unit 29.
In other words, a transistor (or FET) of the nozzle driving unit 29 is turned on in response to an output signal of the AND gate corresponding to the selected nozzle among the nxc3x97m number of AND gates of the signal supply 27.
Therefore, an electric current flows as a driving voltage is supplied to each heating element connected with the turned on transistor (or FET) among the nxc3x97m number of transistors (or FET) to eject the ink through the selected nozzle.
As described above, to discharge the ink from the plurality of nozzles, a large amount of electric current is required.
Recently, the number of nozzles simultaneously discharging the ink in order to perform a high density and printing speed has been increased. Accordingly, a high electric current flows to a power supply terminal Vp of the recording head 273 of the printing unit 270.
As shown in FIGS. 4A-4G, the high electric current flowing to the power supply terminal Vp in order to drive the plurality of the nozzles causes a noise signal to be input to an input signal line (P_data, ADDR). Because the high electric current flows to the recording head 273 within a relatively short period of time, the power supply terminal Vp becomes unstable, and as a result, the noise signal is produced.
Therefore, there is a problem of a malfunction in controlling the nozzles as the noise signal is input into the head driving device together with the data signals.
The present invention has been made to overcome the above and other problems of the related art. Accordingly, it is the object of the present invention to provide an ink-jet printer capable of preventing a malfunction of a head driving device, which is generated when the ink is simultaneously discharged from a plurality of nozzles.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
An ink-jet printer is provided in order to achieve the above and other objects and includes a nozzle driving unit driving a plurality of nozzles to discharge ink, a signal supply supplying a driving signal to the nozzle driving unit, a shift register storing the nozzle selection signal to select a nozzle in response to a recording image after the nozzle selection signal is synchronized with a clock signal, a counter counting an input number of the clock signal and deciding whether to operate the shift register, and a controller inputting a discharge signal to discharge the ink into the signal supply when the shift register is disabled.
The counter compares a set-up value set up in accordance with a predetermined bit number of the nozzle selection data signal and the input number of the clock signal. When the input number is over the set-up value, the shift register is disabled.
On the other hand, a method of driving a head of an ink-jet printer according to an aspect of the present invention includes inputting a nozzle selection data signal to select a nozzle among a plurality of nozzles into a shift register when the nozzle selection data signal is synchronized with a clock signal, disabling the shift register when an input number is above a predetermined value after counting the input number of the clock signal, latching the nozzle selection data signal stored in the shift register, and inputting a discharge signal to discharge ink from the selected nozzle based on the latched nozzle selection data signal.
The latching of the nozzle selection data signal includes resetting a counter counting the input number of clock signals . Therefore, noise generated in the data signal by the discharge signal is eliminated as the discharge signal is input after the nozzle selection data signal is stored into the shift register. Thus a malfunction of head driving device can be prevented.
Moreover, even though the noise signal is generated in the data signal, the malfunction of the head driving device caused by the noise signal can be prevented since the data signal as much as the corresponding bit is input into the shift register by the counter.